From 704b21cb4fa5323564779b1a39b577b2481bf677 Mon Sep 17 00:00:00 2001
From: Nathan Sidwell <nathan@acm.org>
Date: Fri, 21 Jan 2022 11:37:01 -0800
Subject: [PATCH] [demangler] Remove StdQualifiedName

The StdQualifiedName node class is used for names exactly in the std
namespace.  It is not used for nested names that descend further --
those use a NestedName with NameType("std") as the scope.
Representing the compression scheme in the node graph is layer
breaking.  We can use the same structure for those exactly in std too,
and reduce code size a bit.

Reviewed By: ChuanqiXu

Differential Revision: https://reviews.llvm.org/D118249
---
 libcxxabi/src/demangle/ItaniumDemangle.h          | 24 ++++++-----------------
 llvm/include/llvm/Demangle/ItaniumDemangle.h      | 24 ++++++-----------------
 llvm/lib/Demangle/ItaniumDemangle.cpp             |  9 ---------
 llvm/lib/Support/ItaniumManglingCanonicalizer.cpp | 14 -------------
 4 files changed, 12 insertions(+), 59 deletions(-)

diff --git a/libcxxabi/src/demangle/ItaniumDemangle.h b/libcxxabi/src/demangle/ItaniumDemangle.h
index db65c60..b835345 100644
--- a/libcxxabi/src/demangle/ItaniumDemangle.h
+++ b/libcxxabi/src/demangle/ItaniumDemangle.h
@@ -73,7 +73,6 @@
     X(ForwardTemplateReference) \
     X(NameWithTemplateArgs) \
     X(GlobalQualifiedName) \
-    X(StdQualifiedName) \
     X(ExpandedSpecialSubstitution) \
     X(SpecialSubstitution) \
     X(CtorDtorName) \
@@ -1473,21 +1472,6 @@ public:
   }
 };
 
-struct StdQualifiedName : Node {
-  Node *Child;
-
-  StdQualifiedName(Node *Child_) : Node(KStdQualifiedName), Child(Child_) {}
-
-  template<typename Fn> void match(Fn F) const { F(Child); }
-
-  StringView getBaseName() const override { return Child->getBaseName(); }
-
-  void printLeft(OutputBuffer &OB) const override {
-    OB += "std::";
-    Child->print(OB);
-  }
-};
-
 enum class SpecialSubKind {
   allocator,
   basic_string,
@@ -2678,8 +2662,12 @@ AbstractManglingParser<Derived, Alloc>::parseUnscopedName(NameState *State) {
   Node *Result = getDerived().parseUnqualifiedName(State);
   if (Result == nullptr)
     return nullptr;
-  if (IsStd)
-    Result = make<StdQualifiedName>(Result);
+  if (IsStd) {
+    if (auto *Std = make<NameType>("std"))
+      Result = make<NestedName>(Std, Result);
+    else
+      return nullptr;
+  }
 
   return Result;
 }
diff --git a/llvm/include/llvm/Demangle/ItaniumDemangle.h b/llvm/include/llvm/Demangle/ItaniumDemangle.h
index f6acd62..6ac7712 100644
--- a/llvm/include/llvm/Demangle/ItaniumDemangle.h
+++ b/llvm/include/llvm/Demangle/ItaniumDemangle.h
@@ -73,7 +73,6 @@
     X(ForwardTemplateReference) \
     X(NameWithTemplateArgs) \
     X(GlobalQualifiedName) \
-    X(StdQualifiedName) \
     X(ExpandedSpecialSubstitution) \
     X(SpecialSubstitution) \
     X(CtorDtorName) \
@@ -1473,21 +1472,6 @@ public:
   }
 };
 
-struct StdQualifiedName : Node {
-  Node *Child;
-
-  StdQualifiedName(Node *Child_) : Node(KStdQualifiedName), Child(Child_) {}
-
-  template<typename Fn> void match(Fn F) const { F(Child); }
-
-  StringView getBaseName() const override { return Child->getBaseName(); }
-
-  void printLeft(OutputBuffer &OB) const override {
-    OB += "std::";
-    Child->print(OB);
-  }
-};
-
 enum class SpecialSubKind {
   allocator,
   basic_string,
@@ -2678,8 +2662,12 @@ AbstractManglingParser<Derived, Alloc>::parseUnscopedName(NameState *State) {
   Node *Result = getDerived().parseUnqualifiedName(State);
   if (Result == nullptr)
     return nullptr;
-  if (IsStd)
-    Result = make<StdQualifiedName>(Result);
+  if (IsStd) {
+    if (auto *Std = make<NameType>("std"))
+      Result = make<NestedName>(Std, Result);
+    else
+      return nullptr;
+  }
 
   return Result;
 }
diff --git a/llvm/lib/Demangle/ItaniumDemangle.cpp b/llvm/lib/Demangle/ItaniumDemangle.cpp
index 1a5db75..06a74c1 100644
--- a/llvm/lib/Demangle/ItaniumDemangle.cpp
+++ b/llvm/lib/Demangle/ItaniumDemangle.cpp
@@ -404,9 +404,6 @@ char *ItaniumPartialDemangler::getFunctionBaseName(char *Buf, size_t *N) const {
     case Node::KAbiTagAttr:
       Name = static_cast<const AbiTagAttr *>(Name)->Base;
       continue;
-    case Node::KStdQualifiedName:
-      Name = static_cast<const StdQualifiedName *>(Name)->Child;
-      continue;
     case Node::KNestedName:
       Name = static_cast<const NestedName *>(Name)->Name;
       continue;
@@ -446,9 +443,6 @@ char *ItaniumPartialDemangler::getFunctionDeclContextName(char *Buf,
   }
 
   switch (Name->getKind()) {
-  case Node::KStdQualifiedName:
-    OB += "std";
-    break;
   case Node::KNestedName:
     static_cast<const NestedName *>(Name)->Qual->print(OB);
     break;
@@ -550,9 +544,6 @@ bool ItaniumPartialDemangler::isCtorOrDtor() const {
     case Node::KNestedName:
       N = static_cast<const NestedName *>(N)->Name;
       break;
-    case Node::KStdQualifiedName:
-      N = static_cast<const StdQualifiedName *>(N)->Child;
-      break;
     }
   }
   return false;
diff --git a/llvm/lib/Support/ItaniumManglingCanonicalizer.cpp b/llvm/lib/Support/ItaniumManglingCanonicalizer.cpp
index e6cba26..52d5de9 100644
--- a/llvm/lib/Support/ItaniumManglingCanonicalizer.cpp
+++ b/llvm/lib/Support/ItaniumManglingCanonicalizer.cpp
@@ -189,20 +189,6 @@ public:
   bool trackedNodeIsUsed() const { return TrackedNodeIsUsed; }
 };
 
-/// Convert St3foo to NSt3fooE so that equivalences naming one also affect the
-/// other.
-template<>
-struct CanonicalizerAllocator::MakeNodeImpl<
-           itanium_demangle::StdQualifiedName> {
-  CanonicalizerAllocator &Self;
-  Node *make(Node *Child) {
-    Node *StdNamespace = Self.makeNode<itanium_demangle::NameType>("std");
-    if (!StdNamespace)
-      return nullptr;
-    return Self.makeNode<itanium_demangle::NestedName>(StdNamespace, Child);
-  }
-};
-
 // FIXME: Also expand built-in substitutions?
 
 using CanonicalizingDemangler =
-- 
2.7.4